| abstract |
PROBLEM TO BE SOLVED: To provide a positive lithographic printing plate for infrared laser for direct plate making, which is excellent in developing latitude during image formation, suppresses generation of defects due to scratches in an image portion, and can form a good image. Provides a plate making method. SOLUTION: On a hydrophilic support, a lower layer containing a water-insoluble and alkali-soluble resin, and a heat-sensitive layer containing a water-insoluble and alkali-soluble resin and an infrared absorbing dye and having increased solubility in an alkaline aqueous solution by heating are sequentially formed. The laminated positive planographic printing plate precursor is imagewise exposed, and then developed with an alkali developing solution containing a buffering organic compound and a base as main components. |